In this brief article im describing an application of FES (Functional Electrical Stimulation) for breathing support that many may not have seen before - and it features our RehaStim FES unit.
In recent weeks we have had a couple of individuals request from us the means to use this approach at home.
One writes last night -
"I was injured at c5/6 in 1976 aged 16, 36 yrs ago - im now aged 52.
My lung function is quite poor, about 30% of expected efficiency on a recent lung function test.
It has been 30% for 20 years or more but recently, in last 2 years my breathing has worsened. I ‘m not using CPAP at night yet and may have to consider it." Based on experience so far it is certainly worthwhile this individual exploring this FES - enabled approach.
In 2008, Henrik Gollee and clinical colleagues at the Queen Elizabeth National Spinal Injuries Unit in Glasgow, published their exploration of how FES applied to the abdominal muscles could increase the tidal volume and cough peak flow in tetraplegic individuals.
Paralysis of the respiratory muscles in people with tetraplegia affects their ability to breathe and contributes to respiratory complications. Surface FES of abdominal wall muscles can be used to increase tidal volume and improve cough peak flow in tetraplegic subjects who are able to breathe spontaneously.
The stimulation program is intended to provide cyclical stimulation to the abdominal wall muscles with the aim to improve muscle strength and thereby augment respiration.
During breathing, the abdominal muscles are used during exhalation. Thus, stimulation should be applied cyclically during the part of the breathing cycle when the user exhales.
The program provided with the RehaStim therefore periodically applies a stimulation burst to the abdominal muscles. The duration of each stimulation cycle can be adjusted and should match approximately the breathing frequency of the user.
Since stimulation should only be applied during exhalation, a percentage of this cycle can be set during which stimulation is on (usually 50%). Stimulation intensity can be varied by adjusting the pulse width (for all channels). An even stimulation level can be ensured by adjusting the stimulation currents for individual channels to compensate for differences in muscle strength.
In the stimulation protocol four channels are used. Two stimulation channels should be placed medially either side of the umbilicus, whilst two channels are placed laterally with the upper electrode just below the ribs.
As we gain more experience with this in practice I can update this article.
H. Gollee 1, 2, K.J. Hunt 1, 2, D.B. Allan 2, M.H. Fraser 2, A.N. McLean 2
1Centre for Rehabilitation Engineering, University of Glasgow, UK
2Queen Elizabeth National Spinal Injuries Unit, Glasgow, UK
"Automatic electrical stimulation of abdominal wall muscles increases tidal volume and cough peak flow in tetraplegia". Technology and Health care, Vol. 16, No.4, 2008, p 273-281